This blog is produced by members of the School of Politics and International Relation at the University of Nottingham, and by regular guest pieces. The analysis contained in each entry is informed by our internationally-ranked research, and we hope it will help readers better understand the political dynamics that underpin the world in which we all live. The School of Politics and International Relations takes no institutional position and all authors views are their own.

After a summer spent dealing with stumbles, weak campaign messaging and surprisingly strong challenges from other candidates, Hillary Clinton suddenly seems to be back in gear.

Following a sterling debate performance that seems to have already improved her poll numbers, which were already high among Democrats, she displayed her remarkable grit at a gruelling all-day hearing before a committee set up to investigate the 2012 attack in which four Americans were killed in Benghazi, Libya.

The saga over her supposed responsibility for the deaths, which occurred at the end of her tenure as secretary of state, has been unwinding for almost three years. But despite an 11-hour onslaught of sharp personal and political attacks, she skillfully worked to rise above the questions, helping her supporters continue to decry it as a partisan fishing expedition.

Meanwhile, Bernie Sanders’s challenge on her left seems at last to be peaking – and, perhaps most important of all, the sitting vice-president, Joe Biden, has declined to run for office.

Biden’s decision was clearly a reluctant one. It’s obvious he wants to be president. Given he’s served 36 years in the Senate, run for president twice before (in 1988 and 2008) and spent two terms a heartbeat from the Oval Office, it’s hardly surprising he’d want to give the presidency one more go.

But in the end, he clearly concluded he just couldn’t win, saying that the time window to assemble a realistic campaign has closed.

That’s a very sound assessment given the recent history of late entrants to presidential races (think of Rick Perry’s catastrophic effort launched in August 2012).

Biden also had plenty of other vulnerabilities, not least his three and a half decades of senate votes. He has essentially spent his time in the ideological centre of the Democratic Party – and as it has shifted, so has he. He used to support overturning Roe vs Wade, the legal ruling that creates a constitutional right for a women to have an abortion – a vote that would today be anathema among Democrats.

However it would be natural for an incumbent vice-president of a two-term president who’s very popular with his party to be the front-runner for his party’s nomination. The biggest single reason Biden is not running and would have lost if he had, is Hillary Rodham Clinton.

Pulling away

Whatever may have been written about a summer of undeniable stumbles, Clinton is still all but unbeatable in the race for the Democratic nomination. The polls showed she would have been some 35 points ahead of Biden had he run and she’s still at least 20 ahead of the other principal candidate, Bernie Sanders.

This isn’t just a reflection of name recognition of financial heft; she’s enormously popular among Democrats and has high favourability ratings. This is particularly significant for such a well-known figure – people in her case have some knowledge of her already and aren’t just going on name recognition.

Historically perhaps the best indication of a major party nomination has been support among party elites. Clinton has more support than any non-incumbent has enjoyed at this stage of a presidential election, including a majority of Democrats in Congress. By contrast, only three members of congress had said they’d endorse Biden, those being the two senators and lone congressman from his home state of Delaware. In a sense, Biden did not so much bow out as lose a pre-primary battle for the elite support needed to make a run plausible.

Sanders, by far Clinton’s most prominent opponent, is rather more of an outsider. Technically not even a Democrat, he represents Vermont in the US Senate as an independent. He’s running a strong second in the national polls; he has even been outpolling Clinton in the early primary state of New Hampshire and in some surveys he is besting her among self-declared liberal white “Anglos” or non-Hispanics.

But he trails by massive margins among white moderates, blacks and Hispanics. He has shown strength in the first two voting states, Iowa and New Hampshire, not coincidentally two of the whitest states in the US, so may get some early momentum. Even if Sanders were to win both states – which seems to be becoming less likely, not more – he is extremely unlikely to be the Democratic nominee.

The outsider

To win, he has to contend not only with Clinton’s towering strengths, but with his own weaknesses. He has never been a Democrat – and is instead a member of the small and very left-wing Progressive party, under whose banner he has defeated Democratic contenders as recently as 2004.

He is simply too strongly and radically left-wing for Democrat voters. Clinton is closer to the median Democrat office-holder ideologically, whereas Sanders proudly uses the word “socialist” to describe his worldview – a term that even puts off many left-of-centre American voters, and it seems the rest of the public.

Some people apparently see Sanders as simply a “very liberal” Democrat who uses a different label to describe himself, but he’s more complicated than that. On a few significant issues, he has previously voted with Republicans.

Most left-of-centre Democratic voters support a capitalism which is subsidised financially by the state. Sanders’s form of socialism, on the other hand, broadly opposes this at least for large companies. So he voted against the financial crisis bank bailouts and the export-import bank – in the latter case voting against every Democratic Senator.

He’s also less keen than most liberal Democrats on the cause of gun control. Indeed, he initially defeated a moderate Republican in large part thanks to being backed by the NRA. If he continues to rattle Clinton with his surprisingly strong polling and fundraising, expect these “conservative” stances to be brought up more and more.

So if not quite a coronation, Hillary Clinton’s accession to the role of party nominee looks set to be the next best thing. Short of a scandal much bigger than Benghazi currently is, the nomination is hers.

At the same time, her vulnerabilities have not gone away, and the damage of a rough summer has not been completely undone. Her approval ratings have fallen sharply among American voters since she announced her candidacy, and her head-to-head polling against Republican candidates – most of whom are much less well known than her – is not exactly stellar.

So even if the nomination looks hers to lose, the general election could prove to be a much bumpier ride. For now, though, the signs are that Clinton’s path to the nomination is clear.

Tom Packer is a Research Fellow at the Rotheremere American Institute at the University of Oxford. This article was first published on The Conversation and can be found here. Image credit:Brett Weinstein/Flickr.